Even though there are significant advances made in recent years on the technologies of implementing spatial light modulator, there are still limitations and difficulties when employed to provide high quality images display. Specifically, when the display images are digitally controlled, the image qualities are adversely affected due to the fact that the image is not displayed with sufficient number of gray scales. A higher input data rate is required in order to increase the number of gray scales to display the images with sufficient number of gray scales.
For the purpose of illustration, FIG. 1A shows a bit-plane of the image data for displaying images corresponding to the 4-bit grayscales. The time duration represented by the LSB (Least Significant Bit) is the minimum required time to the entire bit plane and is generally referred to as one unit time (1 U). FIG. 1B shows the weight of 4-bit binary data when applied to a pulse-width modulation. The writing process starts from the Most Significant Bit (MSB) to the Least Significant Bit (LSB) and the writing of next bit must be started after completing the writing process of the current bit as indicated by W and the symbol E indicates the end of the writing process.
FIG. 1C is the conventional method to write PWM signal into a 2 dimensional pixel array, where the first data set to be written into a pixel array is the MSB data set containing 1 bit times the number of pixels in the array (if this is a HD TV, 1920×1080=2,073,600 bits. Therefore, it is required to write 1 bit data, i.e., 1 representing an ON state or 0 representing an OFF state, into the entire array, then 128 times the unit time, i.e., 128U, “U” represents the unit time, after the starting time of the first data set writing, the process then starts the writing of the second data set which is the MSB-1, then 64U later from the starting time of the second data set writing, the process then starts the writing of the third data set, and continues down to LSB, 1 times the unit time, i.e., 1U wherein the time length of LSB is 1U by definition. If the LSB is ON, it means the pixel must be ON only for 1U time period. After 1U, the next data, i.e., the MSB may be ON or may be OFF. Therefore, after the LSB is written, it is required to rewrite the pixel after the end of the 1U time period, so that the pixel is ON (or OFF) during LSB (=1U) period.
According to the writing sequence, the writing process must write the entire pixel array in 1U time period. Then the process must rewrite the entire array 1U later. The system speed must be fast enough to write 1 bit of information into each pixel of the entire array. If this is HD-TV, the writing process must be operated to write 1920×1080=2,073,600 bits of data in 1U period. A typical HD-TV refreshes the entire screen 60 times a second. A single panel micromirror represents at least 3 colors in a frame ( 1/60 seconds). If each color is represented in 1/180 seconds with 8 bit gray scale, the entire array must be written at least in 1U=1/(180×256)=21.7 usec for LSB and practically faster than that because there should be allowance of additional time for blanking (unused time between 2 colors). The length of time represented by 1U is 21.7 usec and practically shorter than that. Some image display system allows only one line writing at a time. Only one line at a time can be written the majority of pixel array system is so in the industry. The process to write data for a line must be within 21.7 usec/1080 lines, i.e., must be shorter than 20 nsec. A conventional PWM system requires the speed of data transfer of 20 nsec per line for 8 bit and 1080 line screen. A typical HD-TV contains 1920 pixels per line and this means that 1920 bits have to be transferred to a device in 20 nano-seconds or this equates to 96 Giga bits per seconds. With the present technology, this speed cannot be achieved easily. An improved system is therefore required to reduce the requirement to enable a low cost and small device.
However, the input data rates are limited by the speed of the controller, data transmission rate over the signal lines and the speed of writing data to the memory in each pixel element. Increasing the input data rates by modifying of controller, the signal transmission lines, and memory writing process through hardware modification can be complicate and economically very costly. For these reasons, there are urgent demand to provide new and improved configuration and methods to overcome such difficulties and limitations.